High speed and high load cylinder device

Abstract

A high speed and high load cylinder device is constructed by connecting a piston of a high speed cylinder (1) having a smaller pressure receiving area and a piston of a pressurizing cylinder (2) having a large pressurizing area. The device is provided with a hydraulic circuit for supplying a hydraulic pressure to the high speed cylinder and the pressurizing cylinder. The device has a sequence valve (5) at an intermediate position in a passage (2e) providing in the piston of the pressurizing cylinder for communicating an upper chamber (2 1 ) and a lower chamber (2 2 ) of the pressurizing cylinder for opening and closing the passage depending upon a pilot pressure. A pilot pressure is supplied for closing the sequence valve by supplying the pilot pressure to the sequence valve. A high speed/pressurizing switching valve (12) is provided at an intermediate position in a piping (11) supplying the hydraulic pressure to the upper chamber of the pressurizing cylinder in the hydraulic circuit. The high speed/pressuring switching valve (12) is closed when high speed operation is required, by not submitting the pilot pressure to the sequence valve (5). The high speed/pressurizing switching valve (12) is open when high pressurizing force is required, by supplying the pilot valve to the sequence valve (5). With the construction, it becomes possible to perform high speed operation by the high speed cylinder and operation coping with high load by the pressurizing fluid without providing the external piping and valve.

I claim: 
     
       1. A high speed and high load cylinder device comprising: a high speed cylinder including a first piston disposed therein and having an effective area, and first and second fluid chambers defined in an interior space of said high speed cylinder by said first piston;   a high pressure cylinder including a second piston disposed therein and cooperating with said first piston of said high speed cylinder, said second piston having an effective area which is larger than said effective area of said first piston, and third and fourth fluid chambers defined in an interior space of said high pressure cylinder by said second piston, said second piston defining a communication passage for selectively communicating said third and fourth fluid chambers with each other;   a hydraulic circuit connected to said high speed cylinder and to said high pressure cylinder for supplying hydraulic pressure thereto, said hydraulic circuit including a fluid path communicating with one of said third and fourth fluid chambers for supplying the hydraulic pressure thereto;   first valve means disposed in said communication passage for selectively establishing and blocking communication between said third and fourth fluid chambers;   first valve control means for controlling a position of said first valve means for selectively establishing and blocking communication between said third and fourth fluid chambers, said first valve control means operating said first valve means at an open position in a high speed mode operation and at a closed position in a high load mode operation; and   second valve means disposed in said fluid path for selectively establishing and blocking communication between said hydraulic circuit and said one of said third and fourth fluid chambers, said second valve means establishing communication between said hydraulic circuit and said one of said third and fourth fluid chambers during said high load mode operation.   
     
     
       2. A high speed and high load cylinder device comprising: a high speed cylinder including a first piston having a first effective area, and first and second fluid chambers defined in the interior space of said high speed cylinder by said first piston;   a high pressure cylinder including a second piston cooperating with said first piston of said high speed cylinder and having a second effective area which is greater than said first effective area of said first piston, and third and fourth fluid chambers defined in the interior space of said high pressure cylinder by said second piston, said second piston defining a communication passage for communicating said third and fourth fluid chambers with each other;   a hydraulic circuit connected to said high speed cylinder and to said high pressure cylinder for supplying hydraulic pressure thereto, said hydraulic circuit including a fluid path communicated with one of said third and fourth fluid chambers for supplying the hydraulic pressure thereto;   first valve means disposed in said communication passage for selectively establishing and blocking communication between said third and fourth fluid chambers;   first valve control means, including a pilot pressure source, for controlling a position of said first valve means for selectively establishing and blocking communication between said third and fourth fluid chambers, said first valve control means operating said first valve means at an open position in a high speed mode operation and at a closed position in a high load mode operation; and   said first and second pistons being connected together through an integrated piston rod which defines an axially extending through-opening communicated with said first valve means at one end, the other end of said axially extending through-opening being connected to said pilot pressure source so as to have said first valve control means supply a pilot pressure for placing said first valve means at said closed position during said high load mode operation.   
     
     
       3. A high speed and high load cylinder device comprising: a high speed cylinder having a first piston disposed therein, said first piston having a pressure receiving area;   a pressurizing cylinder having a second piston disposed therein, said second piston having a pressurizing area which is larger than said pressure receiving area of said first piston;   a hydraulic circuit for supplying a hydraulic pressure to said high speed cylinder and to said pressurizing cylinder;   a fluid passage in said second piston for providing communication between an upper chamber and a lower chamber of said pressurizing cylinder by said second piston;   a sequence valve provided at an intermediate position in said fluid passage of said second piston for opening and closing said fluid passage depending upon a pilot pressure;   a pilot pressure source for generating said pilot pressure;   a high speed/pressurizing switching valve provided at an intermediate position in a piping which supplies hydraulic pressure to the upper chamber of said pressurizing cylinder, said high speed/pressurizing switching valve being closed when a high speed operation is required, and at the same time, the pilot pressure not being supplied to the sequence valve, and said high speed/pressurizing switching valve being open when a high pressurizing force is required, for supplying the pilot pressure to the sequence valve.   
     
     
       4. A high speed and high load cylinder device as set forth in claim 3, further comprising: a piston rod which connects together said pistons of both of said high speed and pressurizing cylinders; and   a pilot pressure supply passage defined in said piston rod for supplying the pilot pressure to the fluid passage in the second piston.   
     
     
       5. A high speed and high load cylinder device as set forth in claim 1, wherein said first valve control means controls the position of said first valve means, independent of said first piston.